48 Where are LEDs mainly used? A particular type of LED is the laser diode, which transforms current into a focused beam of light. It is mainly used in CDs, DVDs, fibre optics, barcode scanners, and medical treatment devices. A capacitor takes a shorter time to accumulate electric charge and releases the energy more quickly than a battery. ONLINE RESOURCES Ampli ers and oscillators carbon: carbonio focused: mirato huge: enorme one-way: unilaterale OTHER ELECTRONIC COMPONENTS Diodes, resistors, inductors, and capacitors are called passive electronic components, as they neither produce energy nor provide power gain, but simply absorb energy or store it in the form of voltage or current. A diode is made of two opposite types of semiconductors joined together. It functions as a one-way switch, allowing current to flow easily in one direction, but blocking it from flowing in the opposite direction. In this way, alternating current is changed into direct current; for this reason, diodes are also known as rectifiers. Diodes are mainly used in circuits where a constant control of voltage is needed. Light emitting diodes (LEDs) are particular types of diodes that emit light when current flows through them . Resistors are devices that control the flow of current in a circuit opposing a certain amount of resistance to it and protecting circuits from damage. Resistors are made of carbon or metal oxide and may have different values of resistance. They are used in medical instruments, voltage regulators, and amplifiers. Inductors are made of a coil of wire wound around an iron core. They work on the principle of electromagnetic induction: when current passes through an inductor, 116 ELEcTRONIcS AND ELEcTROTEcHNOLOGY this generates a magnetic field that varies in time, blocking the alternating current and allowing only direct current to flow. Inductors are used in a huge number of electric and electronic devices, such as transformers and electric motors, and in high-frequency AC circuits. Capacitors, or condensers, are circuit components that can temporarily store electrical energy in electronic circuits . They are made of two metal plates with an insulator between them. Capacitors do not allow direct current to pass, but they allow the passage of alternating current. They are mainly used in electronic circuits as filters to regulate the electric charge.